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Dewater the ground????

01-03-2009, 06:07 AM

Here's the scoop; We're building a bridge on a training camp here in VA and the bridge sits on these big concrete blocks. Problem is the the bridge is spanning a river bed and the water table is at 12" below grade. We have to dig down to 6' below grade to build up for the subgrade. The river is currently diverted but the water is still there making it impossible to build a strong base for these blocks to sit on. What's the best way to get the water out of the ground temporarily? Some of our guys know soil stabilization so that's not the issue. They just need the water gone and since I'm a plumber, plumber/water, guess who get's to figure it out.

Or just try driving well points spaced around your work perimeter. Tie them together with some pipe (must be able to withstand suction of pump) into a header and run to your dewatering pump(s). Discharge the water far downhill or some other method to ensure it does not re-enter your excavation.

How big of an area?
Can you treat each block as a separate area?
Is there no one from CEC there to engineer this?

Comment

Driving the steel sheeting is the best bet but can run the cost of the job up alot. You can over dig the width and length. On the sides that you can make a dewatering area that will be dug slightly deeper than your required depth. Base your excavation with trap rock to allow the water to move towards the dewatering areas. You will have pumps set up in the dewatering areas. This all depends on the type of soil you are have, if it is sandy and loose it won't work. The excavation walls will continue to collapse. You can also get a cheap pump to set in the middle of the excavation depending on the excavation size. The pump will be abandoned in place when done. Just some things we have done in the past that might work for you.

Comment

about halve way down it talks about dewatering the hole they had to recover the steamboat Araba that sunk in 1856 in the Mississippi river even tho now it was nearly a mile from the river, http://www.glswrk-auction.com/102.htm
(some pictures of the process at the web site)

As with any new venture problems can quickly develop. The Arabia lay in an old underground river channel below the water level and at the 20 foot level of the dig, water began flowing in. To extract the water so the dig could continue, 20 wells, each about 65 feet deep, were constructed around the hull of the wreck. Each well was made of steel casings and had heavy duty water pumps placed inside. Thousands of feet of steel and plastic pipe were then installed to remove and divert the water away from the excavation site. When working at there peak these pumps would remove as much as 20,000 gallons of water-per-minute, sending it back into the Missouri River, over a half mile away.

Push sticks/blocks Save Fingers
~~~~~~~~~~~~~~~~~~~
"The true measure of a man is how he treats someone who can do him absolutely no good."
attributed to Samuel Johnson
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PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

The first objective was to securely anchor the bridge's two towers on the solid bedrock found under the layers of mud below the East River. A huge wooden caisson, resembling a giant box, was assembled on land, towed to the site of the Brooklyn-side tower and sunk. Compressed air was pumped into the chamber to prevent the surrounding water from leaking in. The caisson's false floor was then ripped out allowing workers to dig up the river bottom.

The working conditions within the caisson resembled a scene from Dante's Inferno. The tremendous pressure, the suffocating heat, the lack of oxygen and the noise all combined to limit a worker's time within the caisson to a maximum of two hours. As they ascended through the compressed air to the top of the caisson, the workers were threatened with the crippling and painful effects of the bends - an imbalance of nitrogen in the blood caused by a too rapid ascension out of the compressed air.

Push sticks/blocks Save Fingers
~~~~~~~~~~~~~~~~~~~
"The true measure of a man is how he treats someone who can do him absolutely no good."
attributed to Samuel Johnson
~~~~~~~~~~~~~~~~~~~
PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

Contact the co. a guy in Your area can install these. 10" galvy helicals driven to refusal
or so many Kips. You can pull and re-use later. Most struct. and many Geo techs. don't have a clue on these. Can be put in with a skid steer. Raised My home on one side 3 1/2"
You have My phone # if needed

I can build anything You want , if you draw a picture of it , on the back of a big enough check .